// Problem: 
// Contest: 
// URL: 
// Memory Limit: 
// Time Limit: 
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
signed main()
{
	int t=1;
//	cin>>t;
	while(t--)
	{
		int n;
		cin>>n;
		vector<int> v;
		for(int i=1;i<=n;i++)
		{
			int x;
			cin>>x;
			int c,l=-INT_MAX;
			for(int j=0;j<x;j++)
			{
				cin>>c;
				if(c<=l)
				{
					cout<<"NO";
					return 0;
				}
				v.push_back(c);
				l=c;
			}
		}
		sort(v.begin(),v.end());
		for(int i=1;i<(int)v.size();i++)
		{
			if(v[i]-v[i-1]!=1)
			{
				cout<<"NO";
				return 0;
			}
		}
		cout<<"YES";
	}
	return 0;
}
